AVS 58th Annual International Symposium and Exhibition
    Thin Film Division Monday Sessions
       Session TF-MoA

Paper TF-MoA9
Conductive Coatings on Nonwoven Fiber Mats by Atomic Layer Deposition

Monday, October 31, 2011, 4:40 pm, Room 107

Session: Emerging ALD Applications
Presenter: William Sweet, North Carolina State University
Authors: W. Sweet, North Carolina State University
J.S. Jur, North Carolina State University
G.N. Parsons, North Carolina State University
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Conductive fiber mats offer unique possibilities in the development of many sensing and protective electronic systems. In this work, atomic layer deposition (ALD) is applied to produce conformal coatings of conductive ZnO on complex fiber systems such as nonwoven polypropylene and nylon. The conductivity of these materials were evaluated using a modified 4-probe method specific for fabric structures and correlated with the overall mass gain of the fabric samples after ALD processing. This analysis provided a detailed evolution of the conductive films on the fabric mats. For example, nonwoven polypropylene coated with ZnO showed a significant initial mass increase, eventually becoming linear with increasing ALD cycles. The corresponding conductivity of these films remained low (< 3 S cm-1), even after 500 ALD ZnO cycles. Inserting a thin insulating ALD Al2O3 layer prior to the ZnO growth, linear ZnO mass gain was achieved after low ALD cycles. Transmission electron microscopy shows that the Al2O3 barrier reduces the penetration of the ZnO vapor phase reactants into the polypropylene. As a result, a higher effective conductivity (> 25 S cm-1) was achieved after 200 ALD ZnO cycles that corresponded well with measurements from simultaneous ZnO growth on a planar silicon oxide surface. For comparison, ZnO deposition on nonwoven nylon-6 exhibits uniform growth without Al2O3 pretreatment and the conductivity again changes significantly with the Al2O3 pretreatment. Implications of the deposition temperature, film thickness, and the use of aluminum doping, on the chemical, mechanical, and electrical properties of ZnO films deposited on polypropylene and nylon nonwovens will be discussed.